This invention relates to a color member or colored article, e.g., a color filter for a multicolor display device, and to a method for manufacturing the color member.
FIG. 1 illustrates an example in which color members are applied as a multicolor filter to a display device. In the drawing, reference numeral 1 denotes a transparent substrate, 2a, 2b and 2c denote display electrodes comprised of a transparent electroconductive film patterned in a desired figure or character, and 3a, 3b and 3c denote colored layers formed on the surface of the display electrode in close contact therewith. The colored layers 3 serve as color filters. Reference numeral 4 denotes a transparent counter electrode, and 5 denotes a transparent opposite substrate. A material which passes or blocks an incident light in response to a voltage applied thereto to function as an optical shutter, such as a liquid crystal or an electrochromic material, is filled in the space defined between the two substrates 1 and 5. If the color filters 3a, 3b and 3c are of mutually different colors, a multicolor display can be provided by selectively applying voltages between the display electrodes 2a, 2b, 2c and the counter electrode 4.
A multicolor display using color filters is very effective in practice, because the method is simple, any color can be obtained easily, and a variety of display materials can be employed in combination with a variety of display systems.
When manufacturing a multicolor display device using color filters, however, care must be taken to prevent any displacement between the pattern of the color filter formed on the surface of the display electrode and the pattern of the display electrode. Particularly, when manufacturing a color graphic display using a fine pattern of three primary colors, a crucial problem from the point of view of the manufacturing process is how to align the pattern of the display electrode with that of the color filters. Color separation among the three primary colors in manufacturing the multicolor display also requires a complicated manufacturing process, and, particularly when the coloring of the display electrodes is achieved by dyeing, a dye resist coating process must be added to prevent portions which have already been dyed from being dyed again by a different dye, so that the dyeing process is even more complicated. In addition, the resist-dyeing technique itself has various problems that must be individually examined according to the kind of dye used.
Screen printing and photolithography are methods generally used for forming the colored layers. Screen printing eliminates the necessity of resist-coating, but there is a limit in making the line pattern. Therefore, the greater the number of colors, the lower the accuracy of the printing position, and the greater the displacement of the resultant colored layer from the display electrode. It is also difficult to produce shading of colors, particularly continuous color shading.
Photolithography can provide a fine pattern, but the photolithography process must be repeated for each color with the necessity of additional resist-coating to prevent re-dyeing during dyeing of the different color. This makes the process so complicated that the merit of this simple coloring method is lost.
As a method of forming a colored layer which can eliminate all the problems described above, the inventors of the present invention previously proposed an electrodeposition method in which a display electrode on a substrate is used as an electrodeposition electrode, and the colored layer is formed from a solution in which an electrodepositable polymer and a dye or pigment are dispersed by using electrodeposition (Japanese Patent Application No. 233,933/1982). In spite of its relative simplicity, this method does not have the problem of pattern displacement even when the patterns are highly miniaturized, and can be used to economically produce a multicolored member with a high colorfastness without the necessity of any specific dyeing process when the colors are changed. If a material which is electrochemically unstable, such as In.sub.2 O.sub.3, is used as an electrode when forming the colored layers in accordance with this method, an oxidation-reduction reaction takes place on the surface of the electrode so that a uniformly colored layer can not be obtained. As a result of studies, the inventors of the present invention have discovered that an electrode made of SnO.sub.2 can provide a uniformly colored layer, but a voltage drop occurs along the electrode. A display electrode of a display device is provided with a display electrode of a fine pattern when SnO.sub.2 alone is used as the transparent conductive display electrode, the voltage drop occurs along the display electrode, because its volumetric resistance is high. Particularly, in a time sharing mode of display drive which requires a high driving frequency, the magnitude of this voltage drop varies according to distance from a lead terminal, and this has an adverse effect on the display quality. The thickness of the SnO.sub.2 film can be increased to reduce its resistance, but the increased thickness greatly reduces the optical transparency of the transparent conductive film.